The present invention relates to a semiconductor device formed of an insulating tape that has an electrically conductive wiring provided to electrically connect a semiconductor chip and external terminals, and particularly to a ball grid array (BGA) type semiconductor device with its external terminals made of spherical solder balls.
A BGA type semiconductor device suitable for multiple pins, small size and high-speed operation has been practically used in order to increase the mounting density of semiconductor devices. The BGA type semiconductor device has solder bumps disposed as its external terminals in a two-dimensional array on the surface of the semiconductor device. In the BGA type semiconductor device, a member called an interposer is also used that has a conductive wiring formed on and/or within its surface in order to electrically connect the semiconductor chip and the external terminals. The interposer is used in a form of a printed wiring board of which the base material is a glass/epoxy resin, or in another form of an insulating tape having a conductive wiring on the surface of a base made of polyimide or the like.
A semiconductor device using the insulating tape with conductive wiring formed is described in xe2x80x9cHigh Connection Reliability Cleared by Structure-Improved CSPxe2x80x9d, Nikkei Microdevice, February, 1998, pp. 48-55. In a conventional BGA semiconductor device as illustrated in FIG. 10, an insulating tape 2 as an interposer is used that has a conductive wiring 4, bonding pads 3, lands 5 and an insulating film 6. A semiconductor chip 1 has its lower side 1b mounted on a semiconductor chip mounting surface 2a of the insulating tape 2 with an adhesive member 8. The bonding pads 3 formed on the semiconductor chip mounting surface 2a of the insulating tape 2 are respectively located within openings 12 that are formed in the insulating film 6. The bonding pads and electrodes formed on the upper surface, 1a of the semiconductor chip 1, though not shown are electrically connected by bonding metal fine wires 7 to those pads and electrodes, respectively. A sealing member, or mold 9 is provided on the chip mounting surface 2a side of the insulating tape 2, sealing the semiconductor chip 1 and the metal fine wires 7. The external terminals, 10 are provided on the mounted side 2b of the insulating tape 2, and bonded to the lands 5 within openings 11 of tape 2. The semiconductor chip 1 and external terminals 10 are electrically connected through the metal fine wires 7, bonding pads 3, conductive wiring 4 and lands 5.
In the conventional semiconductor device shown in FIG. 10, the semiconductor chip 1 is made of a material of silicon (Si) of which the linear expansion coefficient is about 2xcx9c3xc3x9710xe2x88x926/xc2x0 C. The insulating tape 2 is made of a base material such as polyimide resin or glass/epoxy resin of which the linear expansion coefficient is about 10xc3x9710xe2x88x926/xc2x0 C. The sealing mold 9 is chiefly epoxy resin with silica particles filled, and has a linear expansion coefficient of about 8xcx9c14xc3x9710xe2x88x926/xc2x0 C.
The semiconductor device is usually mounted through the external terminals 10 on a printed wiring board or substrate that is made of a base material of a glass/epoxy resin (for example, FR-4) of which the linear expansion coefficient is about 15xcx9c16xc3x9710xe2x88x926/xc2x0 C. The linear expansion coefficient of the whole conventional semiconductor device is close to that of the semiconductor chip 1 because the proportion of the semiconductor chip 1 within the whole semiconductor device is large.
When the semiconductor device mounted on the printed wiring board undergoes a temperature cycle test for reliability, or experiences a temperature change, a distortion is caused at the external terminals 10 made of chiefly a solder material (such as Pbxe2x80x94Sn based eutectic solder or Snxe2x80x94Agxe2x80x94Cu based solder) due to the linear expansion coefficient difference between the semiconductor device and the printed wiring board.
In the conventional semiconductor device shown in FIG. 10, only one side, or the chip mounting side 2a, of the insulating tape 2 is sealed with the sealing mold 9. Therefore, when the temperature is decreased, the semiconductor device is deformed to curve, causing a distortion at the external terminals 10 due to the contraction of the sealing mold 9. The distortion due to the warp is super-imposed on the distortion that is caused by the linear expansion coefficient difference of the semiconductor device to the printed wiring board, thus further increasing the distortion at the external terminals. When the external terminals 10 are greatly distorted and subjected to repetitive temperature changes, they are cracked and finally broken down.
The distortion due to the above factors becomes the largest at the external terminal 10a that is bonded to the land 5a close to the edge of the semiconductor chip 1 of which the linear expansion coefficient is the smallest in the semiconductor device. The breakdown will be most probably caused from this portion. Particularly when the land 5a close to the edge of the semiconductor chip 1 is disposed to extend across the side edge of the semiconductor chip 1 as shown in FIG. 10, a large distortion is caused thereat as will be apparent from the following reason. Although the distortion at such a part of the external terminal 10a as located right under the semiconductor chip 1 can be alleviated by the deformation of the adhesive member 8 that is elastic, the other portion over which there is no semiconductor chip 1 is restricted by the sealing agent 9 and thus cannot be freely deformed. Therefore, a large distortion is concentrated at the end of the external terminal 10a that is located outside the side edge of the semiconductor chip 1, causing it to break down with a high probability.
When the linear expansion coefficient of the sealing agent 9 is not so large, the external terminal 10b located at the edge of the semiconductor device is sometimes distorted greatly, thus broken down with some probability as is similar to the external terminal 10a close to the edge of the semiconductor chip 1.
Occurrence of breakdown of the external terminal 10 will result in electrical disconnection, and therefore the semiconductor device does not properly operate, thus the reliability of the semiconductor device being remarkably reduced.
Accordingly, it is an object of the invention to provide a semiconductor device of particularly BGA type capable of preventing/suppressing the external terminals from being broken down, or having high reliability.
The above object can be achieved by the semiconductor device having, for example, such structures of (A)xcx9c(H) as described below.
(A) A structure having a first insulating member, external terminals provided on a main surface of the first insulating member, a semiconductor chip provided on the opposite side to the side of the first insulating member on which the external terminals are provided, a conductive member for electrically connecting the semiconductor chip and the external terminals, and a sealing member provided on the opposite side to the side of the first insulating member on which the external terminals are provided, wherein a second insulating member is interposed between the semiconductor chip and the first insulating member, and the outer edge of the second insulating member extends from the outer edge of the semiconductor chip.
(B) A structure having a first insulating member, external terminals provided on a main surface of the first insulating member, a semiconductor chip provided on the opposite side to the side of the first insulating member on which the external terminals are provided, a conductive member for electrically connecting the semiconductor chip and the external terminals, and a sealing member provided on the opposite side to the side of the first insulating member on which the external terminals are provided, wherein a second insulating member is interposed between the semiconductor chip and the first insulating member, and the outer edge of the second insulating member extends to a location corresponding to the outer edge of the external terminal that is located outside the outer edge of the semiconductor chip and nearest to the semiconductor chip side.
(C) A structure having an insulating tape including a plurality of bonding pads and lands and a conductive wiring for electrically connecting the bonding pads and the lands, a semiconductor chip, a conductive member for electrically connecting the semiconductor chip and the bonding pads, an adhesive member that is adhesive to the semiconductor chip and provided on the semiconductor chip mounting side of the insulating tape except at least the bonded area of the bonding pads with the conductive member, a sealing member for sealing the surroundings of the semiconductor chip and the conductive member, and external terminals bonded to the lands.
The adhesive member is originally used for mounting the semiconductor chip on the surface of the insulating tape, and therefore usually provided only on the underside of the semiconductor chip. The adhesive member is made of epoxy based resin or polyimide based resin, and these materials are usually more flexible than the insulating tape material. This adhesive member is provided not only on the underside of the semiconductor chip but also on the semiconductor chip mounting side of the insulating tape except the bonding pad region, so that the distortion caused at the external terminals due to the linear expansion coefficient difference between the semiconductor chip and the printed wiring board or substrate can be alleviated by the deformation of the flexible adhesive member. In addition, since the amount of warp of the semiconductor device due to the contraction of the sealing member can be decreased, the distortion caused at the external terminals due to the warp can be reduced.
Moreover, in order to make full use of the flexible property of the adhesive member, it is desirable to make the elastic coefficient of the adhesive member smaller than that of the insulating tape. When the elastic coefficient of the adhesive member is small, the adhesive member itself can be easily deformed to absorb the deformation caused at the external terminals. Thus, the distortion at the external terminals can be reduced more. The elastic coefficient (longitudinal modulus of elasticity) of the insulating tape is about 3000xcx9c9000 MPa. The elastic coefficient of the material of the adhesive member is smaller than that, but it is actually about 1000 MPa.
(D) A structure having an insulating tape including a plurality of bonding pads and lands and a conductive wiring for electrically connecting the bonding pads and the lands, a semiconductor chip, a conductive member for electrically connecting the semiconductor chip and the bonding pads, an adhesive member for gluing the semiconductor chip to the semiconductor chip mounting side of the insulating tape, a sealing member for sealing the surroundings of the semiconductor chip and the conductive member, and external terminals bonded to the lands that are located on both the outside and inside of the edge of the semiconductor chip, wherein the adhesive member is provided to cover a region including at least the lands located outside the edge of the semiconductor chip.
When the lands bonded to the external terminals are provided outside and inside the edge of the semiconductor chip, the adhesive member, which itself is used for mounting the semiconductor chip on the insulating tape surface, is usually provided to cover only the lands located inside the edge of the semiconductor chip, or on the underside of the chip.
Since the adhesive member that is more flexible than the insulating tape is provided not only to cover the lands located on the underside of the semiconductor chip but also the lands located on the outside of the edge of the semiconductor chip, the distortion caused at the external terminals due to the linear expansion coefficient difference between the semiconductor device and the printed wiring board can be alleviated by the deformation of the flexible adhesive member. In addition, since the amount of warp of the semiconductor device due to the contraction of the sealing member can be decreased, the distortion caused at the external terminals due to the warp can be reduced.
Moreover, in order to make full use of the flexible property of the adhesive member, it is desirable to make the elastic coefficient of the adhesive member smaller than that of the insulating tape.
(E) A structure having an insulating tape including a plurality of bonding pads and lands and a conductive wiring for electrically connecting the bonding pads and the lands, a semiconductor chip, a conductive member for electrically connecting the semiconductor chip and the bonding pads, an adhesive member for gluing the semiconductor chip to the semiconductor chip mounting side of the insulating tape, a sealing member for sealing the surroundings of the semiconductor chip and the conductive member, and external terminals bonded to the lands that are located on the outside of the edge of the semiconductor chip, wherein the adhesive member is provided to cover a region including at least the lands located outside the edge of the semiconductor chip.
When the lands bonded to the external terminals are provided outside the edge of the semiconductor chip, the adhesive member, which itself is used for mounting the semiconductor chip on the insulating tape surface, is usually provided only on the underside of the semiconductor chip but not to cover at least the lands located outside the edge of the semiconductor chip.
The adhesive member that is more flexible than the insulating tape material is provided to cover the region including the lands located outside the edge of the semiconductor chip, so that the distortion caused at the external terminals due to the linear expansion coefficient difference between the semiconductor device and the printed wiring board can be alleviated by the deformation of the flexible adhesive member. In addition, since the amount of warp of the semiconductor device due to the contraction of the sealing member can be decreased, the distortion caused at the external terminals due to the warp can be decreased.
Moreover, in order to make full use of the flexible property of the adhesive member, it is desirable to make the elastic coefficient of the adhesive member smaller than that of the insulating tape.
Also, it is desired that the adhesive member be made of a film-shaped material.
There is a method of mounting the semiconductor chip on the surface of the insulating tape, in which the adhesive member is previously provided on the semiconductor chip mounting area of the insulating tape and then the semiconductor chip is bonded through the adhesive member. In this case, the adhesive member is provided by applying a liquid material or a film-shaped material. In order to make effective use of the distortion reducing effect of the adhesive member, it is necessary that the adhesive member be made of a low-elasticity material, and assure a certain useful thickness. This is because the distortion caused at the external terminals due to the linear expansion coefficient difference between the semiconductor device and the printed wiring board is chiefly shearing strain.
The adhesive member according to the application of a liquid material is provided by means of screen printing or potting. However, these means are difficult in controlling the thickness of the adhesive member, and make the manufacturing process complicated.
The adhesive member according to the application of a film-shaped material provides an approximately uniform film thickness, and thus the thickness of the adhesive member after the bonding can be easily controlled. The semiconductor device can also be produced in the same way as in the prior art. The film-shaped adhesive member can be made equal to the thickness of the insulating tape, or to about 50xcx9c80 xcexcm after the bonding of the semiconductor chip. Therefore, the adhesive member can be satisfactorily deformed to effectively reduce the distortion at the external terminals.
(F) A structure having an insulating tape having a plurality of bonding pads and lands and a conductive wiring for electrically connecting the bonding pads and the lands, a semiconductor chip, a conductive member for electrically connecting the semiconductor chip and the bonding pads, an adhesive member for gluing the semiconductor chip to the semiconductor chip mounting side of the insulating tape, a sealing member for sealing the surroundings of the semiconductor chip and the conductive member, and external terminals bonded to the lands, wherein the adhesive member is provided to cover a region including the lands that are located outside the edge of the semiconductor chip and at least close to the edge of the semiconductor chip.
When the conventional semiconductor device shown in FIG. 10 is mounted on a printed wiring board or substrate, the largest distortion is caused at the external terminal 10a close to the edge of the semiconductor chip that has the smallest linear expansion coefficient among the other parts of the semiconductor device. In other words, this external terminal 10a most probably breaks down.
Thus, the flexible adhesive member is provided to cover the region including the lands located close to and outside the edge of the semiconductor chip, so that the distortion caused at the external terminal bonded to this land can be alleviated by the deformation of the flexible adhesive member.
(G) A structure having an insulating tape having a plurality of bonding pads and lands and a conductive wiring for electrically connecting the bonding pads and the lands, a semiconductor chip, a conductive member for electrically connecting the semiconductor chip and the bonding pads, an adhesive member for gluing the semiconductor chip to the semiconductor chip mounting side of the insulating tape, a sealing member for sealing the surroundings of the semiconductor chip and the conductive member, and external terminals bonded to the lands that are located on both the outside and inside of the edge of the semiconductor chip, wherein a member with a lower elastic coefficient than the insulating tape is provided on the semiconductor chip mounting side of the insulating tape and to cover the lands located outside the projected plane of the semiconductor chip.
(H) A ball grid array type structure having an insulating tape having a plurality of bonding pads and lands and a conductive wiring for electrically connecting the bonding pads and the lands, a semiconductor chip, a conductive member for electrically connecting the semiconductor chip and the bonding pads, an adhesive member for gluing the semiconductor chip to the semiconductor chip mounting side of the insulating tape, a sealing member for sealing the surroundings of the semiconductor chip and the conductive member, and external terminals bonded to the lands located outside the edge of the semiconductor chip, wherein a member with a lower elastic coefficient than the insulating tape is provided on the semiconductor chip mounting side of the insulating tape and to cover the lands located outside the projected plane of the semiconductor chip.
Since the flexible low-elasticity member is provided to cover the lands that are located outside the projected plane of the semiconductor chip, the distortion caused at the external terminals due to the linear expansion coefficient difference between the semiconductor device and the printed wiring board can be alleviated by the deformation of the flexible low-elasticity member. In addition, since the amount of warp of the semiconductor chip due to the contraction of the sealing member can be decreased, the distortion caused at the external terminals due to the warp can be reduced.
Since the lands located inside the projected plane of the semiconductor chip are covered by the flexible adhesive member, the distortion caused at the external terminals bonded to the lands inside the edge can be reduced by the distortion alleviating action of the deformed adhesive member.
Furthermore, in order to make full use of the flexible property of the adhesive member and low-elasticity member, it is desired that the elastic coefficients of both materials be smaller than that of the insulating tape. When the adhesive member and low-elasticity member have small elastic coefficients, these members themselves can be easily deformed. Thus, since the deformations of the external terminals can be easily absorbed by the deformations of the adhesive member and low-elasticity member, the distortion caused at the external terminals can be further reduced.
The inventors of the present invention application examined by finite element method how the solder material of which the external terminals are made is distorted when the semiconductor device of the following structure is mounted on a printed circuit board or substrate, and when the ambient temperature is changed from 125xc2x0 C. to xe2x88x9255xc2x0 C. The result was that when the adhesive member was provided inside the projected plane of the semiconductor chip, or beneath the chip, the external terminals close to the edge of the semiconductor chip were distorted 1.5%, while when the adhesive member was provided on both the outside and inside of the projected plane of the semiconductor chip, these external terminals were distorted as low as 1.1%. The specifications of the semiconductor chip used for the analysis are given below.
Size of semiconductor device: 13 mmxc3x9713 mm
Size of semiconductor chip: 8.8 mmxc3x978.8 mm
Number of external terminals: 176
Distance between external terminals: 0.8 mm